1. Field of the Invention
The present invention relates to a silver halide photographic light-sensitive material which excels in sensitivity/graininess ratio and storage stability, which has less color-remaining after having been developed, and which contains methine compounds.
2. Description of the Related Art
In recent years, it has been increasingly demanded that photographic light-sensitive materials provide higher-quality images and have high sensitivity.
To meet the demand, various attempts have been made to increase the sensitivity/graininess ratio of a silver halide emulsion.
(1) JP-B-47-11386, for example, discloses a silver halide photographic light-sensitive material of which the graininess has been improved by the use of mono-dispersed grains. ("JP-B" means Published Examined Japanese Patent Application.)
To increase sensitivity or the like, a sensitizing dye should be absorbed in as great an amount as possible. In the spectral sensitization of a mono-dispersed regular silver halide emulsion, a sensitizing dye, even if suitable for enhancing sensitivity, fails to be dissolved completely out of the silver halide light-sensitive material if added in an increased amount. This results in the problem known as "color-remaining" i.e., coloring of the silver halide photographic light-sensitive material due to the sensitizing dye remaining in the material. Hence, in many cases, a sensitizing dye cannot be added in an amount great enough to make the material exhibit satisfactory properties.
JP-A-64-77047 (corresponding to DE 3819241A), for example, discloses the technique of adding a large amount of a sensitizing dye, thus controlling chemical sensitization, thereby to increase sensitivity. ("JP-A" means Published Unexamined Japanese Patent Application.) Like the technique described above, this technique causes color-remaining, and can hardly be applied to regular silver halide emulsions.
(2) Also, in recent years, many techniques have been disclosed which relate to methods of manufacturing and using tabular silver halide grains. This is because tabular silver halide grains are advantageous in that they may promote color sensitization, improve sensitivity and graininess, and increase sharpness. Among the publications disclosing these techniques are: U.S. Pat. Nos. 4,434,226, 4,439,520, 4,414,310, 4,433,048, 4,414,306, and 4,459,353.
In particular, tabular silver halide grains can have a large amount of a sensitizing dye absorbed to them since each grain has a great surface/grain size ratio (i.e., surface ratio). Hence, they can absorb a great amount of light, possibly increasing sensitivity. If the sensitizing dye is added in a large amount, however, it fails to be dissolved completely out of the silver halide light-sensitive material if added in an increased amount. This results in color-remaining, i.e., coloring of the light-sensitive material due to the sensitizing dye remaining in the material. In consequence, the sensitizing dye cannot be added in a sufficient amount, though it can be absorbed to the tabular silver halide grains.
(3) Further, a number of attempts have been made to enhance the sensitivity of a photographic light-sensitive material, without increasing the grain size of silver halide photographic emulsion. One of them is concerned with a light-sensitive material using an internal latent-image emulsion containing grains internally chemical-sensitized so that an latent image may be formed within each grain as the material is exposed to light. For example, U.S. Pat. Nos. 2,696,436, 3,206,313, 3,917,485, 3,979,213 and 4,623,612, JP-B-43-29405, JP-B-45-13259 describe silver halide photographic emulsions or silver halide photographic light-sensitive materials, which have good photographic properties. These emulsions and these materials have high internal sensitivities since they have been prepared by immersing samples, coated with silver halide emulsions, in an AgNO.sub.3 solution or a silver-halide solvent, or by performing Ostwald ripening or adding an AgNO.sub.3 aqueous solution and a soluble halogen-salt aqueous solution after the chemical sensitization carried out during the preparation of the silver halide emulsions. Although most of these emulsions and materials exhibit high photographic sensitivities if developed with specific internal development solutions, they cannot exhibit sufficient photographic sensitivities if developed with ordinary developing solutions which does not contain, on design, a large amount of a silver halide solvent such as KI or sodium thiosulfate.
Furthermore, U.S. Pat. No. 3,966,476 discloses a silver halide emulsion which forms latent images in the voids opening to the surface of the grain, and can be developed by a surface developer. This emulsion, however, cannot be considered an internal latent-image emulsion; it cannot have excellent photographic properties inherent in an internal latent-image emulsion.
U.S. Pat. Nos. 4,839,268 and JP-A-63-264740 disclose techniques relating to an internal latent-image emulsion which can exhibit a high sensitivity if developed with any of various developing solutions, and also relating to a photographic light-sensitive material using this specific emulsion. In these publications it is described that, if an emulsion is to exhibit a sufficient sensitivity when developed with an ordinary photographic developing solution, two conditions must be satisfied. First, the latent image formed due to exposure must be positioned within a specific distance from the surface of each grain and be formed. Second, a latent image must be formed, to some extent, also on the surface of each grain.
It is known that these internal latent-image emulsions can acquire an optimal minus blue-sensitivity when a relatively great amount of a sensitizing dye is added to it, since its blue sensitivity decreases due to the adsorption of the sensitizing dye, but less than that of a surface latent-image emulsion. When a large amount of a sensitizing dye is added to the internal latent-image emulsion, the sensitizing dye fails to be dissolved completely out of the light-sensitive material, consequently, color-remaining will occur, that is, the light-sensitive material will be colored with the residual sensitizing dye. The greater the amount of the sensitizing dye added, the more prominent the color-stain is. In consequence, the sensitizing dye cannot be added in a sufficient amount, though the addition of a large amount of the sensitizing dye can provide a high sensitivity.
(4) Further, for the purpose of increasing sensitivity, it is desirable that a sensitizing dye be adsorbed in as great an amount as is possible for more intensifying of its adsorption. As is known, the higher the temperature, the more readily a sensitizing dye can be adsorbed to silver halide grains. Some methods have been disclosed, in which a sensitizing dye is added during chemical ripening or during the forming of grains, so that the adsorption of the sensitizing dye is intensified. More specifically, U.S. Pat. No. 4,425,426 disclose methods wherein a sensitizing dye is added before the chemical sensitization or during the chemical sensitization, and U.S. Pat. Nos. 4,225,666, JP-A-61-103149, JP-A-61-133941, and JP-A-61-165751, for example, disclose methods wherein a sensitizing dye is added during the growth of grains, achieving intensified adsorption of the sensitizing dye.
The inventors hereof have been studying the above-described techniques in their effort to enhance the sensitivity/graininess ratio of a silver halide emulsion. They could not, however, achieve their objective since color-remaining occurs by the sensitizing dye which remains in the light-sensitive material after the processing of development because of the intensified adsorption of the sensitizing dye. To solve this problem, it has been proposed that use be made of a sensitizing dye which has hydrophilic substituent groups such as a sulfamoyl group and a carbamoyl group, e.g., the sensitizing dyes disclosed in JP-A-1-147451, JP-A-61-294429, JP-B-45-32749, and JP-A-61-77843. Generally, however, a sensitizing dye will be less readily adsorbed if rendered more hydrophilic. Hence, if the sensitizing dye is made more hydrophilic and thus less liable to remain in the light-sensitive material, it will desorbed from the grains while the light-sensitive material is stored at high temperature and high humidity, inevitably causing desensitization of the sensitizing dye. Although the sensitizing dye disclosed in U.S. Pat. No. 3,282,933 is less liable to cause color-stain, its spectral sensitization power is small, and cannot be achieve both effective spectral sensitization and sufficient control of color-remaining.